Science Class X 1997(CBSE)
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General Instructions :
(i)   All questions are compulsary.
(ii) Question number 1 to 10 are very short answer question,carrying 1 mark each.They are to be answered in one or two sentences.
(iii) Question number 11 to 20 are short answer questions,each carrying 2 marks. Answer to them should not exceed 40 words each.
(iv)  Question numbers 21 to 30 are also short answer questions,each carrying 3 marks. Answer to them should not exceed 60 words each.
(v) Question numbers 31 to 33 are long answer questions,each carrying 5 marks. Answer to them should not normally exceed 100 words each.

Q.1 Name any two semiconductors which are used in the manufacture of solar cells.


Q.2 What are "planetesimlas" ?


Q.3 Name two planets found between the Sun and the Earth.


Q.4 Which has a lower ignition temperature, Kerosene or LPG?


Q.5 An iron knife kept dipped in a blue copper sulphate turns the blue solution light green. Why?


Q.6 Name one metal element and one non-mental element which are obtained on a large scale generally from sea water.


Q.7 Which two of the following compounds could belong to the same homologous series? C₂H₆O₂, C₂H₆O, C₂H₆, CH₄O


Q.8 Arrange the following steps in order of their sequence of occurrence in Nitrogen Cycle starting from nitrogen gas: Ammonification, Denitrification, Nitrification, Nitrogen fixation.


Q.9 Sample of blood of a person, on routine microscopic examination, revealed a high percentage of stippled Red Blood Cells. Name the pollutant responsible for this condition.


Q.10 Two lots of cooked dal are maintained at 30° and 45° C respectively. Which one of these two temperatures is likely to cause spoilage earlier?


Q.11 State two major objectives of the space research programme inour country.


Q.12 "Obtaining of energy from nuclear fusion reactions is preferable to obtaining of energy from nuclear fission reactions". Give tow reasons to justify this statement.


Q.13 A burner when ignited consumes 0.5 g of LPG in 55 seconds. If the calorific value of LPG is 110 KJ/g calculate the energy consumption power of the burner in kW units.


Q.14 Calculate the calorific value of wax in kJ/g units, when 10g of wax of a candle is burnt to heat 1 kg of water from 25°C to 45° C. (Specific heat of water = 4.2 J/g° C)


Q.15 Although hydrogen gas has a very high calorific value still it is not used as an industrial fuel. State four reasons for this.


Q.16 Given a solution of substance A, how will you test whether it is saturated or unsaturated with respect to A, at the prevailing temperature? What is observed when a hot saturated solution of a substance is allowed to cool?


Q.17 Draw a labelled diagram of the apparatus used for the laboratory preparation of Ethene. Write the related chemical equation.


Q.18 An organic compound 'X' which is sometimes used as an anti-freeze, has the molecular formula C2H6O 'X' on oxidation gives a compound 'Y' which gives effervescence with baking soda solution. What can 'X' and 'Y' be? Write their structural formulae.


Q.19 What is meant by 'Ecological Pyramids'? Draw an ecological pyramid having four trophic levels with snake as one of its components.


Q.20 How would you test for the presence of the following adulterants in the food items named? (i) Metanil yellow in gram-dal (ii) Argemone oil in an edible oil.


Q.21 If 768 kJ of energy is produced per hour in a nuclear fission reactor, work out the number of fissions that would be taking place in it in 10 minutes, given that the energy released per fission is 3.2 x 1011J.


Q.22 What is meant by the term "differentiation" ? Describe the major layers of earth with a labelled diagram.


Q.23. What is meant by efficiency of a heat engine ? How much heat energy will have to be supplied to heat engine having efficiency of 30% to lift a mass of 100 kg through a heigh of 30 metres ? (g = 10 m/s2)


Q.24 Name the type of orbits possessed by a remote sensing satellite & communication satellite. Describe their orbits. What is the function of a transponder in a communication satellite ?


Q.25 With the help of diagrams describe the working of a diesel engine. In which stage is th eworking of diesel engine different from that of a petrol engine ?


Q.26 An element has two allotropic forms A and B and belongs to group V of the periodic table. A is much darker in colour than B. Ignition temperature of A is 200°C and that of B is 30°C. What may A and B be? Which one of them reacts with (i) chlorine on heating but not in the cold, (ii) hot concentrated solution of NaOH producing a gas? Write the chemical equations for the reactions involved.


Q.27 "Faulty methods of cooking are responsible for deficiency of nutrition in food." Discuss.


Q.28 Differentiate between biome and biosphere. Why is biosphere considered as a higher level in the organisation?


Q.29 What is hybridisation in relation to crops? Describe the process of hybridisation to produce an improved variety of wheat. Mention one advantage and one disadvantage of a high yield variety of wheat.


Q.30 In a lake contaminated with pesticides, which one of the following organisms living in that lake will contain the maximum amount of the pesticide? Small fish, Zooplanktons, Big fish, phytoplanktons and Water birds. Define the process cited above. Name the substance whose accumulation in pelicans of Lake Michigan led to the formation of thin shells of their eggs.


Q.31 With the help of a diagram, describe the experiment that established the relationship between mechanical energy and heat. Name the scientist who established this relationship. What observations were made by scientist in this experiment ?


Q.32 Described the steps involved in the extraction of aluminium from bauxite using the electrolytic method. Draw a diagram of the electrolytic cell used. Why is some cryolite mixed with purified bauxite in this method?


Q.33 List two basic steps involved in preservation of food. Describe three common methods used for the preservation of fruits and vegetables. Name any two food preservatives commonly used in our country.